There are a number of microfabrication technologies that have been utilized for making microstructures (e.g., micromechanical devices, microelectromechanical devices) by what may be characterized as micromachining, including LIGA (Lithography, Galvonoforming, Abforming), SLIGA (sacrificial LIGA), bulk micromachining, surface micromachining, micro electrodischarge machining (EDM), laser micromachining, 3-D stereolithography, and other techniques. Bulk micromachining has been utilized for making relatively simple micromechanical structures. Bulk micromachining generally entails cutting or machining a bulk substrate using an appropriate etchant (e.g., using liquid crystal-plane selective etchants; using deep reactive ion etching techniques). Another micromachining technique that allows for the formation of significantly more complex microstructures is surface micromachining. Surface micromachining generally entails depositing alternate layers of structural material and sacrificial material using an appropriate substrate (e.g., a silicon wafer) which functions as the foundation for the resulting microstructure. Various patterning operations (collectively including masking, etching, and mask removal operations) may be executed on one or more of these layers before the next layer is deposited so as to define the desired microstructure. After the microstructure has been defined in this general manner, the various sacrificial layers are removed by exposing the microstructure and the various sacrificial layers to one or more etchants. This is commonly called “releasing” the microstructure from the substrate, typically to allow at least some degree of relative movement between the microstructure and the substrate.
It has been proposed to fabricate various types of optical switch configurations using various micromachining fabrication techniques. One of the issues regarding these types of optical switches is the number of mirrors that may be placed on a single die. A die is commonly referred to as that area defined by one field of a stepper (or contact aligner in some instances) that is utilized to lay out the die. In the case of a stepper, die size is generally limited to the maximum optical field size of the stepper, which is typically less than or on the order of 30 mm or so depending on the specific stepper being used. Reducing the size of the mirrors in order to realize the desired number of mirrors on a die may present various types of issues. For instance, there are of course practical limits as to how small the mirrors can be fabricated, or more limiting is the minimum acceptable size of the micromirrors for the optical application, which thereby limits the number of ports for the optical switch for a given die size. Therefore, it may not be possible to fabricate an optical switch with a certain number of ports using a single die. Moreover, as smaller and denser microstructures are incorporated on a die, impact on chip yield may become more and more of an issue. For instance, a microelectromechanical optical switch may be rendered defective during the handling of a chip on which the switch is fabricated as the size of the various microstructures is reduced, and the chip area is increased.